Not a medal I'm knowledgeable in, but one can distinguish authenticity by looking up a original, paying attention to every detail, then vigorously comparing the known original to yours. Make sure to pay very close attention to the Lettering and objects found within the medal. This is usually were errors will be discovered in a reproduction. Good luck with your search and welcome.

Here are two original examples, one made by the Spanish, and the other by the Germans.
You will also find within this thread, again, the known fake which displays the backwards "N". All this was easily found by using the search engine in a matter of seconds.

Wow, I noticed as soon as he got a definitive answer, he signed offline. He was, however, online to see all the comments posted thus far. No please at the beginning, nor a thank you after help was rendered. Oh well, not too uncommon.